A magnetic tape cartridge including magnetic tape with servo information is provided. The servo information comprises a plurality of parallel longitudinal servo bands that lie between a plurality of longitudinal data bands. The plurality of servo bands include odd servo bands and even servo bands, wherein each of the odd servo bands lie between each of the even servo bands. Each of the plurality servo bands include a plurality of frames, wherein each frame includes a plurality of bursts of transition stripes, and each burst having a first transition stripe. The first transition stripe of each burst of each the odd servo band is longitudinally shifted from the first transition stripe of each burst of each even servo band by a substantially equal distance, D, such that servo information of the odd servo bands is interleaved with the servo information from the even servo bands.
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8. A tape cartridge, comprising:
a tape, said tape having servo information comprising:
a plurality of parallel longitudinal servo bands that are positioned between a plurality of longitudinal data bands;
said plurality of servo bands comprise odd servo bands and even servo bands;
each of said plurality servo bands comprising a plurality of frames, wherein each frame comprises a plurality of bursts of transition stripes, each burst having a first transition stripe;
said first transition stripe of each burst of each said odd servo band is longitudinally shifted from said first transition stripe of each burst of each said even servo band by a substantially equal distance, D, such that said servo information of said odd servo bands is interleaved with said servo information from said even servo bands; and
wherein said odd servo bands provide servo information at a first time and said even servo hands provide servo information at a second time such that a servo sampling rate is doubled,
wherein said frame further comprises a first burst of transition stripes in a first azimuthal orientation and a second burst of transition stripes in a second azimuthal orientation different than said first azimuthal orientation, followed by a third burst of transition stripes in said first azimuthal orientation and a fourth burst of transition stripes in said second azimuthal orientation and wherein a distance between said first transition stripe of said first burst and said first transition stripe of said third burst is a distance b,
wherein 0.45B≦D≦0.55B.
6. A magnetic tape cartridge, comprising:
a magnetic tape, said magnetic tape having servo information comprising:
a plurality of parallel longitudinal servo bands that lie between a plurality of longitudinal data bands;
said plurality of servo bands comprise odd servo bands and even servo bands, wherein each of said odd servo bands lie between said each of said even servo bands;
each of said plurality servo bands comprising a plurality of frames, wherein each frame comprises a plurality of bursts of transition stripes, each burst having a first transition stripe;
said first transition stripe of each burst of each said odd servo band is longitudinally shifted from said first transition stripe of each burst of each said even servo band by a substantially equal distance, D, such that said servo information of said odd servo bands is interleaved with said servo information from said even servo bands; and
wherein said odd servo bands provide servo information at a first time and said even servo bands provide servo information at a second time such that a servo sampling rate is doubled,
wherein said frame further comprises a first burst of transition stripes in a first azimuthal orientation and a second burst of transition stripes in a second azimuthal orientation different than said first azimuthal orientation, followed by a third burst of transition stripes in said first azimuthal orientation and a fourth burst of transition stripes in said second azimuthal orientation and wherein a distance between said first transition stripe of said first burst and said first transition stripe of said third burst is a distance b,
wherein 0.45B≦D≦0.55B.
1. A magnetic tape cartridge, comprising:
a magnetic tape, said magnetic tape having servo information comprising:
a plurality of parallel longitudinal servo bands that lie between a plurality of longitudinal data bands;
said plurality of servo bands comprise odd servo bands and even servo bands, wherein each of said odd servo bands lie between said each of said even servo bands;
each of said plurality servo bands comprising a plurality of frames, wherein each frame comprises a plurality of bursts of transition stripes, each burst having a first transition stripe;
said first transition stripe of each burst of each said odd servo band is longitudinally shifted from said first transition stripe of each burst of each said even servo band by a substantially equal distance, D, such that said servo information of said odd servo bands is interleaved with said servo information from said even servo bands; and
wherein said odd servo hands provide servo information at a first time and said even servo bands provide servo information at a second time such that a servo sampling rate is doubled,
wherein said frame further comprises a first burst of transition stripes in a first azimuthal orientation and a second burst of transition stripes in a second azimuthal orientation different than said first azimuthal orientation, followed by a third burst of transition stripes in said first azimuthal orientation and a fourth burst of transition stripes in said second azimuthal orientation and wherein a distance between said first transition stripe of said first burst and said first transition stripe of said third burst is a distance b,
wherein said magnetic tape is configured for a tape drive having a plurality of servo read elements, said first transition stripe of each burst of each said odd servo band is longitudinally shifted from said first transition stripe of each burst of each said even servo band by said substantially equal distance, D, wherein
0.9b/X≦D≦1.1b/X and wherein X is a number servo read elements of said tape drive.
2. The magnetic tape cartridge of
3. The magnetic tape cartridge of
4. The magnetic tape cartridge of
5. The magnetic tape cartridge of
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Commonly assigned U.S. Pat. No. 5,689,384 is incorporated for its showing of a timing based servo system.
This invention relates to a tape cartridge having a servo pattern, and more particularly, to a magnetic tape of the tape cartridge having timing based servo band(s) extending in the longitudinal direction of the magnetic tape.
Magnetic tape provides a means for physically storing data which may be archived or which may be stored in storage shelves of automated data storage libraries and accessed when required. The reading and/or writing of data in bands on magnetic recording tape requires precise positioning of a magnetic head. The magnetic head must be moved to, and maintained centered over, specific longitudinal data bands, as the magnetic tape is moved longitudinally past the magnetic head. The magnetic head is translated between bands in a lateral direction with respect to the longitudinal data bands.
A servo system is employed to move the magnetic head to and position the magnetic head in the center of the desired data band or bands, and to track follow the center of the desired data band or bands. The data bands are becoming increasingly smaller and closer together in order to increase the data band density and thereby increase data capacity of a given tape. Hence, it has become desirable to place the longitudinal defined servo bands at various locations across the full width of the tape, separated by groups of data bands. This allows the servo bands to be close to the data bands and limits offsets due to tape stretch, etc. This also allows a greater number of bands to be employed due to the greater precision of the relationship between the servo bands and the data bands.
A magnetic tape cartridge including magnetic tape with servo information is provided. The servo information comprises a plurality of parallel longitudinal servo bands that lie between a plurality of longitudinal data bands. The plurality of servo bands include odd servo bands and even servo bands, wherein each of the odd servo bands lie between each of the even servo bands. Each of the plurality servo bands include a plurality of frames, wherein each frame includes a plurality of bursts of transition stripes, and each burst having a first transition stripe. The first transition stripe of each burst of each the odd servo band is longitudinally shifted from the first transition stripe of each burst of each even servo band by a substantially equal distance, D, such that servo information of the odd servo bands is interleaved with the servo information from the even servo bands.
The frame includes a first burst of transition stripes in a first azimuthal orientation and a second burst of transition stripes in a second azimuthal orientation different than the first azimuthal orientation, followed by a third burst of transition stripes in the first azimuthal orientation and a fourth burst of transition stripes in the second azimuthal orientation and wherein a distance between the first transition stripe of the first burst and the first transition stripe of the third burst is a distance B. In one embodiment the second azimuthal orientation is opposite of the first azimuthal orientation.
In one embodiment the magnetic tape is configured for a tape drive having a plurality of servo read elements, the first transition stripe of each burst of each the odd servo band is longitudinally shifted from the first transition stripe of each burst of each the even servo band by a substantially equal distance, D, wherein
and wherein X is a number servo read elements of the tape drive.
Accordingly, in one embodiment the magnetic tape is configured for a tape drive having two servo read elements such that 0.45B≦D≦0.55. In another embodiment the magnetic tape is configured for a tape drive having three servo read elements such that 0.30B≦D≦0.37B.
In one embodiment the magnetic tape comprises five parallel longitudinal servo bands. Further the frame may further include a first burst of a group of five stripes in a first azimuthal orientation and a second burst of a group of five transitions in a second azimuthal orientation different than the first azimuthal orientation, followed by a third burst of a group of four transition stripes in the first azimuthal orientation and a fourth burst a group of four transition stripes in the second azimuthal orientation.
The following is intended to provide a detailed description of an example of the invention and should not be taken to be limiting of the invention itself. Rather, any number of variations may fall within the scope of the invention which is defined in the claims following the description.
Referring to
In the specific example of
The head assembly 24 comprises a plurality of read and/or write elements 28 configured to read and/or write data on a magnetic tape with respect to sets of the longitudinal data tracks 29. In the example of
Those skilled in the art will recognize that the dark slanted stripes represent magnetized areas of recorded magnetic flux that extend across the width of a servo track 27, and that the edges of the stripes comprise flux transitions that are detected to generate a servo read element signal. The transitions have two magnetic polarities, on each edge of a stripe. When a servo read element crosses a transition of servo track 27, e.g. along servo track centerline 50 of
The lateral positioning of the servo read element with respect to the timing based servo track is sensed based on a measure of time between two transitions having different slants, called the “A” distance, as compared to the time between two transitions having parallel slants, called the “B” distance. Referring to
More specifically, lateral position sensing within a defined servo band is achieved by deriving a ratio of these two servo pattern intervals. In particular, the lateral position may be the ratio of (1) the distance between transitions of bursts 40 and 41, called the “A” distance, to (2) the distance between transitions of burst 40 and 42, called the “B” distance. The distances are measured by the timing between the transitions at a constant velocity. Thus, as the tape head servo read elements 25, 26 move toward the lower edge of the tape 20, the ratio of the time between the transitions of burst 40 and 41 to the time between the transitions of bursts 40 and 42 becomes greater, since the distance between the “A” transitions of the burst 40 and 41 is greater, while the distance between the “B” transitions of burst 40 and 42 remains unchanged.
It is important to note that the servo tracks 27 are typically generated by a servo writer having two spaced apart write elements of different slants, forming the “A” distance, which are pulsed simultaneously. Thus, the “A” geometric distance is determined photolithographically, and is therefore, independent of the timing or the velocity of the servo writer drive.
The tape is moved longitudinally across the head assembly 24 so that the servo tracks 27a and 27b are moved across the servo read elements 25 and 26, respectively. When such movement occurs, the servo pattern of magnetic flux transitions is detected by the servo read elements 25 and 26 so that it generates two analog servo read element signals, one for each servo read element 25 and 26. The analog servo read element signals for each servo read element 25 and 26 are provided via a servo signal lines 84 and 90 to signal decoders 86 and 92, respectively. The respective signal decoders then process the servo read element signals and generate a position signal that is transmitted via position signal lines 88 and 94 to servo controller 80. The servo controller 80 generates a servo control signal and provides it on control line(s) 82 to a servo positioning mechanism at head assembly 24. The servo positioning mechanism responds to the control signal from the servo controller 80 by moving the assembly including servo read elements 25 and 26 laterally with respect to the servo track centerline 50 to reach the desired servo track or to maintain the servo read elements 25 and 26 center with respect to the servo track centerline 50.
Servo detection logic of servo system 80 is configured to detect from the signals supplied on line(s) 82, the relative timings of the laterally extending transitions, specifically including the transitions having different slants, sensed by the plurality of laterally spaced servo read elements 25 and 26 as the magnetic tape 20 is moved in the longitudinal direction. The servo detection logic is configured to determine from the relative timings of the sensed transitions the “A” distances and information regarding the relationship between the plurality of servo read elements 25 and 26 and the magnetic tape for at least one known set of laterally extending transitions having differing slants.
Similar to that described with respect to
In the example illustrated in
As illustrated in
Servo read element 25 (as shown in
Furthermore, as illustrated in
The sample rate, Fs, of the servo read element signal is determined by the length of the servo pattern and the tape velocity. The sampling rate, Fs may be expressed as:
wherein the velocity is the velocity of the magnetic tape and the distance is the distance between two transition lines of the servo pattern.
For example, assuming a tape velocity of 2 m/sec, a distance “A” of 50 μm, and a distance “B” of 100 μm, the servo read elements 25 and 26 would output servo information at a rate of 20,000 samples every second.
The sample rate required for proper serving is determined by the rest of the components of the track-following servo loop. In order to support a high bandwidth track following the servo control system requires a high sampling rate servo feedback signal. The high sampling rate provides up-to-date, accurate information of the servo read element position, and therefore, supports a higher servo bandwidth and thus a much better controlled servo system. As the magnetic tape 20 velocity slows to match with the slower data transfer host system (referred to as speed matching) the sampling rate becomes slower and results in too slow of a sampling rate to maintain high bandwidth track following system.
Thus, what is presented is tape cartridge having a servo pattern with a higher longitudinal density of servo information such that a higher servo sampling rate is realized. The higher sampling rate provides up-to-date accurate information of servo read element position and, therefore, ensures a higher servo bandwidth system with increased control.
In accordance with the present disclosure
The magnetic tape 320 is also provided with guard bands 348, 349 at the edges of the tape. The longitudinal direction is defined as the direction along the length of the magnetic tape 320. The lateral direction is defined as the direction along the width of the magnetic tape 320 and is perpendicular to the longitudinal direction.
In the example of
The head assembly 324 comprises a plurality of read and/or write elements 328 configured to read and/or write data on a magnetic tape with respect to sets of the longitudinal data tracks 329. When the servo read elements 325, 326 are properly positioned at the defined servo bands 327, the read and write elements 328 are properly positioned to transfer data with respect to the data track location of the magnetic tape 320.
The lateral positioning of the servo read element with respect to the timing based servo track is sensed based on a measure of time between two transitions having different slants, called the “A” distance, as compared to the time between two transitions having parallel slants, called the “B” distance. Referring to
More generally, lateral position sensing within a defined servo band is achieved by deriving a ratio of these two servo pattern intervals. Specifically, the lateral position may be the ratio of (1) the distance between transitions of bursts 340 and 341, called the “A” distance, to (2) the distance between transitions of burst 340 and 342, called the “B” distance. The distances are measured by the timing between the transitions at a constant velocity. Thus, as the tape head servo read elements 325, 326 move toward the lower edge of the magnetic tape 320, the ratio of the time between the transitions of burst 340 and 341 to the time between the transitions of bursts 340 and 342 becomes greater, since the distance between the “A” transitions of the burst 340 and 341 is greater, while the distance between the “B” transitions of burst 340 and 342 remains unchanged.
As illustrated in
Similar to that described with respect to
In the example illustrated in
As illustrated in
Servo read element 325 measures the “A” distance along servo band 327a by detecting a signal as it crosses a transition stripe of a first azimuthal orientation of servo band 327a (e.g. transition stripe L2) along servo track centerline 350 and then by detecting a signal as it crosses an adjacent transition stripe of a second azimuthal orientation of servo band 327a (e.g. transition stripe L3). Similarly, servo read element 326 measures the “A” distance along servo band 327b by detecting a signal as it crosses a transition stripe of a first azimuthal orientation of servo band 327b (e.g. transition stripe M2) along servo track centerline 350 and then by detecting a signal as it crosses an adjacent transition stripe of a second azimuthal orientation of servo band 327b (e.g. transition stripe M3). Since the transition stripes L3 and M3 are longitudinally shifted from each other by a distance “D”, the servo read element 325 outputs servo information regarding distance “A” at a different time than when servo read element 326 outputs information regarding distance “A” such that the servo information of the odd servo bands is interleaved with the servo information from the even servo bands. Accordingly, servo information obtained from servo element 326 regarding an odd servo band is not provided simultaneously with the servo information obtained from servo element 325 regarding an even servo band.
Furthermore, as illustrated in
Distance “D” may be expressed by the following equation, wherein X is the number of laterally spaced servo read elements of magnetic tape drive:
wherein X is the number of laterally spaced servo read elements of a magnetic tape drive configured to read and/or write to magnetic tape 320. Equation 1 may be simplified as follows:
In one embodiment, tape 320 is to be utilized in a magnetic tape drive having two laterally spaced apart servo read elements 325, 326. In this embodiment the first transition stripe of each burst of each odd servo band is longitudinally shifted from the first transition stripe of each burst of each even servo band by a substantially equal distance “D”, wherein D is between 0.45B and 0.55B. In a further embodiment the distance “D” is approximately 0.50B. Therefore, in the embodiment in which two servo read elements read two different servo bands (e.g. 327a and 327b) the head assembly 324 will output servo information for the even servo band 327a at a different time than that of any adjacent servo band (e.g. odd servo band 327b). Similarly, servo read element 325 will output servo information for the odd servo band 327b at a different time than that of any adjacent servo bands (e.g. 327a and 327c). Therefore, each burst of transition stripes within the odd servo bands (e.g. 327b and 327d) is longitudinally shifted or is offset from each burst of transition stripes of the even servo bands (e.g. 327 a, 327c, and 327e) such that the servo information of said odd servo bands is interleaved with the servo information from the even servo bands. The above described pattern provides a sampling rate that is doubled over the prior art pattern.
For example in the present embodiment, assuming a tape velocity of 2 m/sec and wherein distance “A” is 50 μm, and distance “B” is 100 μm, the servo read elements 325 and 326, would output servo information at a rate of 40,000 samples every second because the odd servo band pattern is shifted longitudinally shifted from the even servo pattern by a distance of “D”, wherein 0.45B≦D≦0.55B.
Returning to
Servo detection logic of servo controller 380 is configured to detect from the signals supplied on line(s) 382, the relative timings of the laterally extending transitions, specifically including the transitions having different slants, sensed by the plurality of laterally spaced servo read elements 325 and 326 as the magnetic tape 320 is moved in the longitudinal direction. The servo detection logic is configured to determine from the relative timings of the sensed transitions the “A” distances and information regarding the relationship between the plurality of servo read elements 325 and 326 and the magnetic tape for at least one known set of laterally extending transitions having differing slants.
A magnetic tape drive 100 is illustrated in
Although the magnetic tape 320 is constrained laterally by the tape guide rollers 110, some minor lateral movement may still occur at the head assembly 324. Further, the magnetic tracks may have some minor lateral movement on the magnetic tape. A servo system 380 is configured to move the head assembly 324, comprising the servo read elements 325 and 326 and read and/or write heads 328 of
Magnetic tape cartridge 103 is illustrated in further detail in
As discuss above, the magnetic tape 320 of tape cartridge 103, has servo information in prerecorded magnetic longitudinal servo tracks for track following at these positions. Each burst of transition stripes within the odd servo bands (e.g. 327b and 327d) is longitudinally shifted or is offset from each burst of transition stripes of the even servo bands (e.g. 327 a, 327c, and 327e) by a substantially equal distance “D” as defined by Equation 2 above.
Since the transition stripes are longitudinally shifted from each other by a distance “D”, the servo read element 325 outputs servo information regarding distance “A” at a different time than when servo read element 326 outputs information regarding distance “A”. Similarly, the servo read element 325 outputs servo information regarding distance “B” at a different time than when servo read element 326 outputs information regarding distance “B”. Accordingly, servo information obtained from servo element 326 regarding an odd servo band is not provided simultaneously with the servo information obtained from servo element 325 regarding an even servo band. Therefore, the servo information of the odd servo bands is interleaved with the servo information from the even servo bands.
In one embodiment the distance “D” is between 0.45B and 0.55B. In a further embodiment the distance “D” is 0.50B. The above described pattern on a magnetic tape 320 of tape cartridge 103 provides a sampling rate that is doubled over the prior art patterns.
For example, in the present embodiment, assuming a tape velocity of 2 m/sec, a distance “A” of 50 μm, and a distance “B” of 100 μm, the servo read elements 325 and 326, would output servo information at a rate of 40,000 samples every second since the odd servo band pattern is shifted longitudinally shifted from the even servo pattern by a distance of “D”, wherein 0.45B≦D≦0.6B.
While the above described embodiment discusses a head assembly comprising two servo read elements, a head assembly may comprise any number of servo elements. For example, in another embodiment, the head assembly 324 comprises three servo read elements, (325, 326, and 330) as shown in
For example, each burst of transition stripes of servo band 327b will be shifted longitudinally a distance “D” of approximately 0.33B from each burst of transition stripes of servo band 327a. Similarly, each burst of transition stripes of servo band 327c will be shifted longitudinally a distance “D” of approximately 0.33B from each burst of transition stripes of servo band 327b. Further, each burst of transition stripes of servo band 327d will be shifted longitudinally a distance “D” of approximately 0.33B from each burst of transition stripes of servo band 327c such that the transition stripes of servo band 327d is aligned with the transition stripes of servo band 327a. Finally, each burst of transition stripes of servo band 327e will be shifted longitudinally a distance “D” approximately 0.33B from each burst of transition stripes of servo band 327d such that the transition stripes of servo band 327e is aligned with the transition stripes of servo band 327b.
Similar to that discussed above with respect to
For example, in the present embodiment, assuming a tape velocity of 2 msec, a distance “A” of 50 μm, and a distance “B” of 100 μm, the servo read elements, 325, 326, and 330, would output servo information at a rate of 60,000 samples every second since each burst of transition stripes within one servo band is shifted or is offset a substantially equal distance “D” from the burst of transition stripes of the previous servo band, wherein 0.30 B≦D≦0.37B.
It should be understood by one of ordinary skill in the art that while the above description describes magnetic transition stripes recorded on magnetic tape, it should be understood that the servo bands 327 may comprise any of several types of longitudinal servo patterns as is known to those of skill in the art.
While the present embodiment describes servo bands 327a, 327c, and 327e as even servo bands and 327b, and 327d as odd servo bands, it should be understood by one of ordinary skill in the art that 327a, 327c, and 327e may be defined as odd servo bands and 327b, and 327d may be defined as even servo bands. Rather, it is only important that each burst of transition stripes within one servo band (is longitudinally shifted or is offset from each burst of transition stripes of any adjacent servo band by a substantially equal distance, “D”.
Further, while the present disclosure describes a magnetic tape 320 having five servo bands and four data bands, the present disclosure may be practiced on any magnetic tape having a plurality of servo bands.
The logic discussed above may comprise any suitable logic arrangement known to those of skill in the art. Further, those of skill in the art will understand that differing specific component arrangements may be employed than those illustrated herein.
While particular embodiments of the present invention have been shown and described, it will be obvious to those skilled in the art that, based upon the teachings herein changes and modifications may be made without departing from this invention and its broader aspects and, therefore, the appended claims are to encompass within their scope all such changes and modifications as are within the true spirit and scope of this invention. Furthermore, it is to be understood that the invention is solely defined by the appended claims.
Bui, Nhan Xuan, Ogura, Eiji, Tsuruta, Kazuhiro, Hancock, Reed Alan
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